Patent GB-509259-A (GB)
Title: Improvements in or relating to means for metering the consumption of a liquid or liquid fuel by a power unit
IPC: G01F3/20
Filed: 1938-01-12
Abstract: 509,259. Liquid meters; valves; mercury switches. PARFITT, A. W. (Adams, A. H.). Jan. 12, 1938, No. 1018. [Classes 69 (i), 69 (ii) and 135] [Also in Group XXXVII] A liquid meter, particularly for measuring the fuel consumption of a power unit, comprises a diaphragm or membrane movable in a measuring chamber to effect a predetermined change of volume in it, means for summing the diaphragm movements, and means for feeding the liquid alternately to the two sides of the diaphragm comprising a change-over valve positively and automatically operated by an external source of power independent of the flow of the liquid. The meter shown comprises a lenticular measuring chamber formed by dished perforated plates 3, 4 secured in a housing 6, the volume of the chamber being accurately adjustable by screws 15 bearing on the two plates. A flexible membrane 12 is secured at its edges between the plates or walls 3, 4 and is caused by the fluid admitted to one side of the housing 6 and passing through one of the perforated plates 3, 4 to lie snugly against the other, as shown. The fluid is admitted alternately to either side of the housing, each admission causing the membrane to move across the measuring chamber until it comes into contact with the opposite wall, when a volume of fluid equal to that of the measuring chamber will have passed through the meter. The flow of fluid is controlled by a slide valve 20 operated by solenoids 90, 91 and formed with grooves 38 co-operating with ports leading to the two sides of the housing 6 and to fuel inlet and outlet passages 34, 35 respectively. A poppet-valve which may alternatively be used is also described. In either case the solenoids are energised alternately to reverse the valve by means of a mercury switch, Fig. 5, in which the rise of pressure occurring in the fluid being metered when the membrane 12 comes to rest against one wall of the measuring chamber acts through ports 62 or 63 on a flexible diaphragm 65, the depression of which increases the pressure on one or the other side of a drop of mercury in a passage 70 and causes it to move past a constriction 79 in the passage from one to the other of two pairs of contacts 74, 76 and 75, 77. The passage 70 and the passages 68, 69 connecting it to the underside of the diaphragm 65 are preferably filled with an inert gas, or a circuit-breaking oil or other liquid. The switch also controls the circuit of an electricallyoperated counter, which may be graduated to indicate the quantity of fuel remaining in the tank; when non-interconnected tanks are used a separate counter is employed for each and is switched into circuit when the fuel-supply line is connected to the corresponding tank. To avoid interruption of the fuel-supply at the moment the change-over valve 20 operates, the inlet and outlet passages 34, 35 are connected to the spaces on each side of a diaphragm 102 stretched across a chamber 100. In the case of failure of current in the valve circuits a solenoid 114, which normally maintains a valve 110 closed, allows this valve to open and by-pass the fluid around the meter.